zeros at x = -6 (double zero) and x = +3
so we really have
(x+6)(x+6)(x-3)

It is negative for large negative x
it comes up and bounces off the x axis at x=-6, dropping down negative again
it does not actually come up and cross the x axis until x = 3
from then on it is positive,
therefore negative for
x</= +3 except for touching zero at x = -6